Slew bearings are used, for example in open-pit mining equipment to enable the superstructure of such equipment to rotate in relation to the lower frame; they are constructed with a diameter up to several meters. The circular ball race in which the supporting balls run between the upper and lower parts of the ball race --i.e., between the superstructure and the lower frame--, has an oil lubrication system. Merely for economic considerations, oil losses must be kept as low as possible. Environmental protection also demands a construction which is substantially free from oil losses. In the prior art ball race slewing gear permanently plastic mastic or two-component silicone rubber is introduced into grooves of round cross-section in the separating lines between the segments in order to seal the ball race, which is usually made up of four to six, but also even up to twelve segments. Even with a construction which is at first (upon initial construction) satisfactory with respect to sealing tightness, due to unavoidable slight movements of the segments in relation to one another at the separating lines, sealing-tightness is reduced, so that as operations continue, leakage take place. No improvement, such as permanent sealing, results even by application of hand-cut rubber sections. Environmental protection requirements demand the detection of any leakages which may occur and their elimination. This can make considerable expense, since the superstructure must be lifted off the lower frame and the ball race parts dismantled and reassembled. Since as a rule the ball race lower part has an external sealing ring and an internal oil collecting ring, or vice-versa, these members must also be dismounted before the segments are separated from one another, for the introduction of a fresh seal.